Field of the Invention
The present invention relates to a multiple charged particle beam lithography apparatus and a multiple charged particle beam lithography method, and relates to a multiple beam lithography apparatus and method which performs correction of position deviation caused by, for example, distortion of a stage and distortion of a mirror for position measurement.
Related Art
Lithography technique facilitating development of miniaturization of semiconductor devices is a very important process of generating a unique pattern in semiconductor manufacturing processes. In recent years, with high integration of LSIs, line widths of circuits required for semiconductor devices have been miniaturized year after year. In order to form a desired circuit pattern on the semiconductor devices, a highly-accurate master pattern (also called a reticle or a mask) is required. Herein, since an electron beam (EB) lithography technique has an essentially excellent resolution, the EB lithography technique is used to produce a highly-accurate master pattern.
For example, there is a lithography apparatus using one beam. For example, there is a raster-type lithography apparatus. In the raster-type lithography apparatus, for example, one beam is formed from an electron beam emitted from an electron gun assembly through a mask having one hole, and blanking control is performed so that necessary sites are irradiated with the beam while the one shaped beam is deflected by a deflector so as to perform sequential tracing on a target object.
Besides, for example, there is a lithography apparatus using multiple beams. In comparison with the case of lithographing with one electron beam, many beams can be irradiated at one time by using the multiple beams, and thus, the throughput can be greatly improved. In the multiple beam type lithography apparatus, for example, the multiple beams are formed from an electron beam emitted from an electron gun assembly through a mask having a plurality of holes; and with respect to each of the multiple beams, blanking control is performed, each beam which is not blocked is reduced by an optical system, is deflected by a deflector, and is irradiated on a desired position on a target object.
In a lithography apparatus including multiple beam lithography, there is a case of using a laser measurement device at the time of measuring a position of a stage. In the laser measurement device, there is a problem in that error occurs in the measured position due to distortion of a reflecting surface of a mirror disposed on the stage. If distortion occurs in the target object surface which is set as a lithography object, there is a problem in that error occurs in a lithographing position. In the related art, for example, a vector-type single-beam lithography apparatus such as a variable shaping type lithography apparatus, since a coordinate system of the lithography apparatus is corrected into an ideal coordinate system, the entire surface of a to-be-lithographed target object is divided in a mesh shape with predetermined grid dimensions, and a position of the vertex of each mesh is measured. The coordinate system of the lithography apparatus is corrected from an error between the measured position and the design position (this function is called a “grid matching collection (GMC)” function. Hereafter, correction by this function is called GMC correction). More specifically, a pattern for GMC measurement is lithographed at positions corresponding to the positions of the vertexes of the meshes in a mask blank applied with resist. By performing processes such as development and etching on the mask, a position accuracy from the lithographed pattern is measured. The coordinate system of the lithography apparatus is corrected from the obtained result (for example, refer to JP-A-2008-085120). In the GMC correction, the position correction is performed for every shot after shot data are generated.
On the other hand, in the multiple beam lithography type, since many beams are irradiated at one time and the entire multiple beams are deflected collectively even in case of deflecting the beams, it is difficult to correct the positions of the individual beams. In order to correct the positions, there is a method of transforming a pattern shape so as to be fitted to a bit (pixel) pattern, calculating a dose of each pixel, and performing dose such as distributing the dose of the pixel of interest to adjacent pixels. However, in this method, since the dose of the pixel located at an end of the pattern is distributed to surrounding pixels, the steepness of slope of a beam profile disappears (becomes small). As a result, there is a problem in that the resolution is deteriorated. If the resolution is deteriorated, accuracy in lithography position and line width of the pattern is deteriorated.
As described above, in the multiple beam lithography, it is difficult to individually correct position deviations caused by distortion of the reflecting surface of the mirror on the stage and/or the distortion on the target object surface which is set to as the lithography object. As a result, it is difficult to sufficiently correct the position deviations.